wrote in message
. org...
jitter back and forth.

It is not a mechanical switch. The pulse generator consists of an IR
LED that shines on IR sensor with a plastic disk in between that has a
series of black stripes painted around the edge of it. When the wind
cups spin, the disk spins so the black stripes interrupt the IR path
between transmitter and sensor generating pulses. The pulses then to go
to a base of a transistor that I assume is a switching transistor that
is either fully on or fully off. It is an NPN transistor in common
emitter configuration and the output of that is fed directly into the
CPU for counting the pulses in a given time frame for wind speed
determination.

If the disk happens to stop partially blocking the IR transmission path, you
might get random pulses...

Probe the signal at both the input and output of the NPN transistor.
That'll tell you if it's the sensor, the transistor, or the CPU which is
causing the issue.